The Acquisition, Tracking and Pointing (ATP) technology is one of the key technologies in the free space laser communications system. This paper analyzes the ATP theory, and obtained results from experiment. The key parameters of the experimental system are: (1) beacon divergence, 2α b=5 mrad; (2) receiver field of view, 2β ω=10 mrad; (3) angular coverage, 2α≥±1°, 2β≥±1°. The results of the experimental demonstration show that the system can work well in the distances of 1.6～5.0 km. The results accurately match the theoretical analysis.